There is a worldwide pandemic of obesity with far-reaching consequences for the health of our nation. Obesity is the second leading cause of preventable death in the United States. Prevention of obesity, especially in children, has been deemed by public health policy makers to be one of the most important objectives for our country. Obesity disproportionately affects citizens of minority and low socioeconomic status. A consensus of opinion has formed that the recently observed increased prevalence of obesity is caused by environmental and behavioral factors that favor easy access to high calorie foods and sedentary behavior. This prevention project, called LA Health, will test whether modification of these environmental and behavioral factors can prevent inappropriate weight gain in children who are enrolled in the fourth to sixth grades during Year 1. The primary aims of the LA Health project are to test the efficacy of two school-based approaches for obesity prevention. The two approaches are derived from two NIH-funded pilot studies called the HIPTeens project (a secondary prevention program) and the Wise Mind project (a primary prevention program). The study will test the efficacy of primary prevention alone and a combination of primary and secondary prevention in comparison to a no-intervention control group using a cluster randomization research design, with 18 school clusters randomly assigned to the three treatment arms. The project will collaborate with a USDE funded project, LA GEAR UP, to test the relative efficacy of obesity prevention programs for children who come from economically disadvantaged environments. The LA GEAR UP program is designed to enhance educational achievement. Since LA GEAR UP will be implemented in all 18 schools, all of the intervention arms, including no-intervention, will be combined with an academic enhancement program. The study will span three years and will provide critical tests of strategies that modify the child's environment as a primary prevention strategy and provide health behavior modification via classroom instruction and internet counseling as a secondary prevention strategy. The study will also recruit a similar (but smaller) sample of students to measure changes in body weight relative to height, gender, and age over the same three-year period. This observation only control group will be studied to evaluate secular trends in changes in body weight so that body weight changes observed in the randomized trial can be interpreted within the context of stable versus unstable population changes in body weight. The results of this investigation will significantly impact public health policy related to obesity prevention in rural communities, minority communities, and in children from families that are economically disadvantaged.